HOW IT WORKS

HOW IT WORKS; Streaming Onto the Movie Screen, With Nary a Scratch

By KAREN J. BANNAN

Published: May 9, 2002

THE movie theater experience isn't the same for everyone. Sure, the popcorn is probably comparable in most theaters and the seats are, too, but the quality of the image on the screen can vary. Yet today there is a technology that can bring near-perfect movie quality to theaters everywhere: digital projectors.

Currently nearly all movies projected in theaters are film prints, which are delicate and can be scratched or damaged. Movie film quality can thus degrade quickly, especially if the film is shown on a dirty or misaligned projector.

A movie can show signs of scratches and dirt after only a week of screenings, said Phil Livingston, a vice president of Panasonic Broadcast and Television Systems. ''Film gets scratched and the light shining through the film causes the colors to change,'' he said.

Digital projectors do not have such problems. They create images not by shining light through film, but by taking a stream of digital data representing the red, green and blue values of each pixel of each frame and converting it to pulses of colored light.

There are two kinds of large-venue digital projector technology: DLP Cinema, developed by Texas Instruments, and D-ILA, or Digital-Direct-Drive Image Light Amplifier, by JVC. They use the same kind of data files but differ in the way they project them.

DLP creates a picture on the screen by sending a stream of light from a high-powered light bulb through a prism. There, the light is separated into three beams of colored light: blue, green and red. Each beam is focused onto its own digital micromirror device, which uses millions of tiny pivoting mirrors to create the pixels, or dots of color, that make up an image. The light is sent back through the prism, where it is assembled and sent out through a lens and onto the screen.

''The closest analogy is thinking about a blimp hovering over a football stadium where audience members hold up a colored card to create an image,'' said Doug Darrow, a business manager at DLP Products, the commercial entertainment group at Texas Instruments. ''As all of the people in the stadium flip their cards over, they create an image or a logo. That's what we're doing -- constantly flipping these little mirrors that are one-fifth the width of a human hair and doing it 50,000 times a second.'' JVC's system relies on a liquid crystal display instead of mirrors.

Although digital projectors are so far found in only a handful of theaters, many filmmakers, movie studios and film distributors are enthusiastic about the new technology for a variety of reasons.

Distribution costs drop considerably when a studio switches from film prints to digital data. A two-hour print costs from $1,500 to $2,000, fits on six reels and weighs more than 60 pounds. Digital film files are created once and can be duplicated endlessly without incurring additional costs.

What's more, there are usually no shipping costs. Digital movies can be delivered on DVD discs but also over a broadband connection or via satellite, in real time. A two-hour movie takes about two hours to download to the theater's video server. Then it is transmitted to projectors on an in-theater network.

Digital advocates say that the real reason to switch is quality. The images don't jump or wiggle as those projected from film often do. That makes for a clearer picture, even though it is not as sharp or richly colored as a pristine film is, said Bill Dill, senior filmmaker-in-residence at the American Film Institute Conservatory in Los Angeles.

''The blacks are not as black and colors don't have the same dynamic range,'' Mr. Dill said. ''I'm not saying that the digital image is somehow inherently not as good; the digital image is simply different.''

There are other benefits to digital projection. For example, multiplexes with sold-out shows could add more screenings at the last minute.

The chief obstacle to the spread of digital technology is the expense. It costs about $150,000 to convert a theater to digital projection. Theater owners would like the movie studios to help pay for the conversions because the studios benefit from reduced distribution costs. The studios are also concerned that digital films, distributed electronically, would be far easier to pirate.

Still, with filmmakers like George Lucas now keen on releasing their films in digital format, said Ken Williams, president of Technicolor Digital Cinema, a distribution company, it is only a matter of time before many theaters make the change.

Photos (Texas Instruments); (Juan Velasco/The New York Times); Tip of a pin on the surface of a digital micromirror device Chart: ''It's All Done With Mirrors'' By eliminating the need for costly, cumbersome and delicate film prints, digital projectors offer several advantages for movie studios, distributors and theater owners. But few have been in-stalled in cineplexes around the United States so far, largely because of high cost. Here's a look at one digital projector technology, DLP Cinema, developed by Texas Instruments. 1) Light from a powerful xenon bulb is split by a set of prisms into red, green and blue beams. 2) Each colored beam is directed to a separate digital micromirror device, a chip that contains 1.3 million tiltable mirrors, each a fraction of a micron wide. Each mirror represents a pixel. With some modifications, existing film projector lamp housings could be used with a digital projector head. 3) A processor sends a stream of digital data for each color to the corresponding micromirror array. The data contains grayscale information for each pixel (essentially, how bright each is) for each frame of the movie. 4) The zeros and ones in the data cause the micromirrors to tilt. Depending on a mirror's position, light is either reflected into the projection lens or deflected away from the lens. In this way, each mirror acts as a switch, turning the light on or off. 5) The red, blue and green light reflecting off the mirrors recombines and is projected through the lens, forming the range of colors that make up the image. The grayscale image The mirror array is using basic semconductor fabrication techniques. Each mirror tilts independently, when a small voltage is removed, the mirror tilts the other way. This can happen many thousands of times per second. Micromirror device The mirror array is made using basic semiconductor fabrication techniques. techniques Each mirror tilts independently, when a small voltage is applied. When the voltage is removed, the mirror tilts the other way. This can happen many thousands of times per second. (Sony Pictures Entertainment Digital Inc.)